Mechanically flexible magnetic resonance coil with opening conductor structures

ABSTRACT

The present embodiments relate to a local coil for a magnetic resonance tomography system, the local coil including an antenna element that includes a releasable connection to form an opening.

This application claims the benefit of DE 10 2010 033 322.0, filed onAug. 4, 2010.

BACKGROUND

The present embodiments relate to a magnetic resonance tomography (MRT)local coil for an MRT system.

MRT devices for examining objects or patients using magnetic resonancetomography (e.g., MRT, MRI) are known, for example, from DE10314215B4.

In MR tomography with a magnetic resonance tomography device (MR orMRT), images with a high signal to noise ratio (SNR) may be recordedusing local coils. The local coils are antenna systems positioned indirect proximity on (anterior) or below (posterior) the patient. Duringan MR measurement, excited nuclei in the individual antennas of thelocal coil induce a voltage that is amplified using a low-noisepreamplifier (e.g., LNA, preamp) and forwarded by cable to an electronicreceive system. To improve the signal to noise ratio even withhigh-resolution images, high-field systems are used (e.g., 1.5 T to 12 Tand more). Since more individual antennas may be connected to an MRreceive system than there are receivers present, a switching matrix(e.g., RCCS) is incorporated between receive antennas and receivers.This routes the currently active receive channels (e.g., the receivechannels present in the field of view (FoV) of the magnet at the time)to the receivers present. This allows more coil elements to be connectedthan there are receivers present, since for whole body coverage, onlythe coils present in the FoV or the homogeneity volume of the magnet areto be read out.

A “coil” or a “local coil” may be, for example, an antenna system thatmay include one or a plurality (e.g., in the case of an array coil) ofantenna elements (or “coil elements”). These individual antenna elementsmay be configured as loop antennas (loops), butterfly coils or saddlecoils. A coil includes, for example, the coil elements, a preamplifier,further electronics (e.g., baluns) and cabling, a housing and mayinclude a cable with a plug (e.g., used to connect the coil to the MRTsystem). A receiver (RX) on the system side filters and digitizes asignal received from the local coil and transmits the digitized signalto a digital signal processor that may derive an image or a spectrumfrom the measurement. The digital signal processor may make the image orthe spectrum available to the user for diagnosis purposes.

In interventional radiology, for example, it is possible or advantageousto perform imaging (e.g., MR imaging) using local coils and theintervention at the same time or almost at the same time, or at least toleave intervention instruments (e.g., needles, catheters, ablationinstruments, biopsy needles) and coils set up in positions during theindividual work steps. The coils may cover access to the patient to someextent. With coils that permit mechanical openings between the antennastructures, imaging and intervention may take place through the opening,and an antenna that encloses (e.g., surrounds) the site of theintervention is even advantageous for image quality.

According to the prior art, for example, two coils are each disposed tothe side of the access point so that the two coils may also be removedlaterally (e.g., by pushing to the side and/or in the x direction) whenan instrument (e.g., person, animal) that extends out of the examinationobject in a direction orthogonal to the plane of a coil (and/or the ydirection) is present in the examination object.

SUMMARY

The present embodiments may obviate one or more of the drawbacks orlimitations in the related art. For example, magnetic resonancetomography local coils for an MRT system may be optimized.

The present embodiments optimize local coils (e.g., not only local coilsfor interventional radiology and/or imaging between interventions).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of one embodiment of a magneticresonance tomography (MRT) local coil on a patient in an MRT system;

FIG. 2 shows a schematic diagram of an instrument in one embodiment ofan MRT local coil on a patient;

FIG. 3 shows a schematic diagram of one embodiment of an MRT local coil;

FIG. 4 shows a schematic diagram of one embodiment of an MRT local coilwith an antenna having an opening option in the form of a galvaniccontact;

FIG. 5 shows a schematic diagram of one embodiment of an MRT local coilwith an antenna having an opening option in the form of a capacitivecontact;

FIG. 6 shows a schematic diagram of a circuit for one embodiment of anMRT local coil with an opening option in the form of a capacitivecontact according to FIG. 5; and

FIG. 7 shows a schematic and simplified diagram of an MRT system.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 7 shows an imaging magnetic resonance device MRT 101 (e.g., in ashielded room or Faraday cage F) with a whole body coil 102 with, forexample, a tubular space 103, into which a patient couch 104 (e.g., apatient bed) holding a body 105 (e.g., of an examination object such asa patient; with or without a local coil arrangement 106) may be moved inthe direction of arrow z in order to generate recordings of the patient105 using an imaging procedure. Positioned on the patient, for example,is a local coil arrangement 106 that may be used to generate recordingsin a local region (e.g., a field of view). Signals from the local coilarrangement 106 may be evaluated by an evaluation facility (e.g.,elements 115, 117, 119, 120, 121) of the magnetic resonance device MRT101 that may be connected, for example, by way of coaxial cable or byradio (e.g., elements 167, 168) to the local coil arrangement 106 (e.g.,being converted to images, stored or displayed).

In order to use the magnetic resonance device MRT 101 to examine thebody 105 (e.g., the examination object or the patient) using magneticresonance imaging, different magnetic fields, the temporal and spatialcharacteristics of which are matched as closely as possible, areradiated onto the body 105. A powerful magnet (e.g., a cryomagnet 107)in a measuring cabin with, for example, the tunnel-type opening 103generates a static powerful main magnetic field B₀, of, for example, 0.2Tesla to 3 Tesla or even more. The body 105 to be examined is supportedon the patient couch 104 and moved into a roughly homogeneous region ofthe main magnetic field B0 in the field of view FoV. The nuclear spin ofatomic nuclei of the body 105 is excited by way of magnetichigh-frequency excitation pulses B1(x, y, z, t) that are radiated in viaa high-frequency antenna (and/or optionally, a local coil arrangement)illustrated in FIG. 7 in a highly simplified manner as a body coil 108(e.g., a high-frequency antenna; a multipart body coil 108 a, 108 b, 108c). High-frequency excitation pulses are generated, for example, by apulse generating unit 109 that is controlled by a pulse sequence controlunit 110. After amplification by a high-frequency amplifier 111, thehigh-frequency excitation pulses are routed to the high-frequencyantenna 108. The high-frequency system shown in FIG. 7 is only indicatedschematically. More than one pulse generating unit 109, more than onehigh-frequency amplifier 111 and a plurality of high-frequency antennas108 a, b, c may be used in a magnetic resonance device 101. The magneticresonance device 101 also includes gradient coils 112 x, 112 y, 112 zthat are used during a measurement to radiate in magnetic gradientfields for selective layer excitation and local encoding of themeasurement signal. The gradient coils 112 x, 112 y, 112 z arecontrolled by a gradient coil control unit 114 that, like the pulsegenerating unit 109, is connected to the pulse sequence control unit110.

Signals emitted by the excited nuclear spins (of the atomic nuclei inthe examination object) are received by the body coil 108 and/or atleast one local coil arrangement 106, amplified by assignedhigh-frequency preamplifiers 116 and further processed and digitized bya receive unit 117. The recorded measurement data is digitized andstored as complex numerical values in a k-space matrix. Amultidimensional Fourier transformation may be used to reconstruct anassociated MR image from the value-populated k-space matrix.

With a coil that may be operated in both transmit and receive mode(e.g., the body coil 108 or a local coil), correct signal forwarding isregulated by an upstream transmit/receive switch 118.

An image processing unit 119 uses the measurement data to generate animage that is displayed to a user by way of an operating console 120and/or is stored in a storage unit 121. A central computer unit 122controls the individual system components.

In MR tomography, images with a high signal to noise ratio (SNR) may berecorded using local coil arrangements (e.g., coils, local coils). Thelocal coil arrangements are antenna systems that are positioned indirect proximity on (anterior), below (posterior) or in the body. Duringan MR measurement, the excited nuclei induce a voltage in the individualantennas of the local coil, the induced voltage being amplified using alow-noise preamplifier (e.g., LNA, preamp) and being forwarded to anelectronic receive system. To improve the signal to noise ratio evenwith high-resolution images, high-field systems are used (e.g., 1.5 Tand more). If more individual antennas may be connected to an MR receivesystem than there are receivers present, a switching matrix (e.g.,RCCS), for example, is incorporated between receive antennas andreceivers. This routes the currently active receive channels (e.g., thereceive channels present in the field of view of the magnet at the time)to the receivers present. This allows more coil elements to be connectedthan there are receivers present, since for whole body coverage, onlythe coils present in the FoV or the homogeneity volume of the magnet areto be read out.

The local coil arrangement 106 may be, for example, an antenna systemthat includes, for example, one or, in the case of an array coil, aplurality of antenna elements (e.g., coil elements). The individualantenna elements are configured, for example, as loop antennas (e.g.,loops), butterfly coils or saddle coils. The local coil arrangement 106includes, for example, coil elements, a preamplifier, furtherelectronics (e.g., baluns), a housing, supports and may include a cablewith plug used to connect the local coil arrangement 106 to the MRTsystem. A receiver 168 on the system side filters and digitizes a signalreceived from the local coil 106 (e.g., by radio) and transmits thedigitized signal to a digital signal processing facility that may derivean image or spectrum from the data obtained by measurement. The digitalsignal processing facility may make the image or the spectrum availableto the user (e.g., for the purposes of subsequent diagnosis and/or forstorage).

Possible details of exemplary embodiments of magnetic resonancetomography (MRT) local coils are described in more detail below withreference to FIGS. 1-6.

FIG. 1 shows a cross-section through one embodiment of an MRT local coil106 on a patient 105 in an MRT 101.

FIG. 2 shows a schematic diagram of an interventional or surgicalinstrument N (e.g., a needle, a cannula, a clip, a retainer or a clamp)that extends through an antenna element A2 of one embodiment of an MRTlocal coil 106 (e.g., having an opening O2 in a closed state) and ispresent in a patient 105, the MRT local coil 106 (e.g., a breast coil,an abdomen coil, a leg coil, an arm coil, or a head coil) being located,for example, on or below the patient 105.

The interventional or surgical instrument N is supported by a holder Hof suitable shape (e.g., C-shaped), for example, on a couch 104 oranother system. The materials of the coil, the holder and theintervention instruments may be non-magnetic or minimally magnetic.

The local coil 106 includes one or more antenna elements A1, A2, A3(e.g., circular or approximately square antenna elements) in a housing Gthat is, for example, flexible and/or made of foam. Each of the one ormore antenna elements A1, A2, A3 includes an opening O1, O2, O3 (e.g.,enclosed/surrounded on a periphery by the antenna element) in aconductor track plane (x-z) of the antenna element A1, A2, A3. At leastone surgical element may be passed through each of the openings O1, O2,O3.

FIG. 3 shows a schematic diagram of one embodiment of the MRT local coil106 with the opening O2 in the opened state (e.g., in the form of alateral opening U). Two parts T1, T2 are held away from one another toform an opening U (e.g., a lateral opening) in the opened state so thatan instrument N may be moved out of the local coil 106 (e.g., throughopening O2 of the antenna element A2; moved laterally) in the x-z plane(e.g., without removing the local coil 106 from the patient).

FIG. 4 shows a schematic diagram of one embodiment of an MRT local coil106 with an antenna A2 having an opening option U with a separablegalvanic contact (St-Bu) between two subregions T1, T2 of the antennaA2. The opening option U includes a plug-type connection with a plug(e.g., St) and a socket (e.g., Bu), each in a subregion T1, T2 of thelocal coil 106 (e.g., the antenna element A2 of the).

FIG. 5 shows a schematic diagram of one embodiment of an MRT local coil106 with an antenna A2 having an opening option U using a capacitivecontact between two subregions T1, T2 of the antenna A2, a capacitiveconnection, in which a part C1-bottom and C2-top of a capacitive elementC1 (e.g., a capacitor) is disposed respectively in one of the tworeleasable subregions T1, T2 of the antenna element A2, being provided.

FIG. 6 shows a schematic diagram of an exemplary embodiment of a circuitfor one embodiment of an MRT local coil with an opening option in theform of a capacitive contact according to FIG. 5. The circuit may beconnected via a preamplifier V to an evaluation facility of an MRT.

One embodiment according to FIG. 3 includes a mechanical and electricalopening capacity of conductor structures of at least one antenna element(e.g., with respect to a conductor loop and a housing of the at leastone antenna element) of, for example, a mechanically flexible localcoil. In the opened state of the antenna element, the opening allowsaccess to the patient in at least one intermediate space (e.g., anopening) between the conductors. In one embodiment, connecting methodsthat are suitable for employment in a sterile environment may be used.

According to one embodiment, the local coil 106 is set up so that one ormore antenna elements A2 (e.g., center antenna element according to FIG.3) are set up so that conductor structures L2 of the one or more antennaelements are interrupted by a releasable connection (e.g., U and/orSt-Bu and/or C1top-C1bottom and/or T1-T2). A connection point, forexample, establishes a releasable electrical contact. This releasableelectrical contact may be configured, for example, according to FIG. 4as a galvanic coupling (e.g., metal on metal) or according to FIG. 5, asa capacitive or inductive coupling. The galvanic connection may beestablished mechanically as a pin, a coaxial plug, a pushbuttonconnection or a joint. The capacitive connection may be configured inthe form of two faces that are moved into a defined position in relationto one another due to the mechanical structure. The mechanical structureis configured, for example, so that a form-fit connection between upperand lower pails becomes possible. The two faces may be pressed againstone another by way of a screw, a clip, a lever mechanism, pins, buttons,hooks and other form-fit connections.

A non-galvanic structure has the advantage that the connection pointsare easy to clean, as the faces may also be part of the dielectric ofthe capacitor. With the capacitive coupling solution, the capacitanceresulting at the contact point may also be configured as part of thecapacitance of the series resonant circuit provided by the receive coil.

The opening contact U may be used at one point on the coil or at aplurality of points to open a plurality of antennas A1, A2, A3 of thelocal coil.

The entire local coil may be configured as a mechanically flexible coilto allow optimum molding to the geometry of the patient.

All the cited possible details of exemplary embodiments of the MRT localcoils may be provided individually or in any combination.

While the present invention has been described above by reference tovarious embodiments, it should be understood that many changes andmodifications can be made to the described embodiments. It is thereforeintended that the foregoing description be regarded as illustrativerather than limiting, and that it be understood that all equivalentsand/or combinations of embodiments are intended to be included in thisdescription.

1. A local coil for a magnetic resonance tomography system, the localcoil comprising: an antenna element that includes a releasableconnection to form an opening.
 2. The local coil as claimed in claim 1,wherein the releasable connection is between two parts or subregions ofa conductor loop of the antenna element to form the opening.
 3. Thelocal coil as claimed in claim 1, wherein the releasable connection iswithin a conductor loop, a power circuit of the antenna element, or theconductor loop and the power circuit of the antenna element.
 4. Thelocal coil as claimed in claim 2, wherein the antenna element, in astate, in which the releasable connection between the two parts withinthe antenna element is unopened, includes a conductor loop closed in oneplane.
 5. The local coil as claimed claim 1, wherein, when thereleasable connection is released, the opening is formed between twosubregions of the antenna element held away from one another by therelease of the releasable connection.
 6. The local coil as claimed inclaim 1, wherein, when the releasable connection is released, theopening is formed between two parts of the antenna element held awayfrom one another by the release of the releasable connection, andwherein an instrument is passable through the opening.
 7. The local coilas claimed in claim 1, wherein the local coil comprises an elastichousing, the antenna element comprises a conductor loop, or the localcoil comprises the elastic housing and the antenna element comprises theconductor loop, and wherein the elastic housing, the conductor loop, orthe elastic housing and the conductor loop are operable to hold awayparts of the antenna element from one another to form the opening. 8.The local coil as claimed in claim 7, wherein the elastic housingcomprises flexible plastic, foam or a joint, with which one of the partsis fastened to the remainder of the elastic housing.
 9. The local coilas claimed in claim 1, comprising a plurality of antenna elements, theplurality of antenna elements comprising the antenna element, whereinthe releasable connection is provided in a center antenna element of theplurality between two subzones of the center antenna element, the centerantenna element being between two antenna elements of the plurality. 10.The local coil as claimed in claim 1, wherein the releasable connectioncomprises a galvanic connection between two subregions of a conductorloop of the antenna element.
 11. The local coil as claimed in claim 1,wherein the releasable connection comprises a mechanically releasableconnection within a power circuit of the antenna element.
 12. The localcoil as claimed in claim 1, wherein the releasable connection comprisesa plug-type connection between two releasable parts of the antennaelement, and wherein a housing of the local coil is operable to hold thetwo releasable parts away from one another.
 13. The local coil asclaimed in claim 1, wherein the releasable connection comprises acapacitive connection between two releasable parts of the antennaelement, and wherein a part of a capacitive element of the capacitiveconnection is disposed in one of the two releasable parts of the antennaelement.
 14. The local coil as claimed in claim 1, comprising aplurality of antenna elements, the plurality of antenna elementscomprising the antenna element.
 15. The local coil as claimed in claim1, wherein the releasable connection is provided at only one point inonly the antenna element.
 16. The local coil as claimed in claim 1,wherein the releasable connection is provided at a plurality of pointsin only the antenna element or in a plurality of antenna elements, theplurality of antenna elements comprising the antenna element.
 17. Thelocal coil as claimed in claim, wherein the local coil, the antennaelement, or the local coil and the antenna element are mechanicallyflexible.
 18. The local coil as claimed in claim 4, wherein theconductor loop is a galvanically or capacitively transmitting conductorloop.
 19. The local coil as claimed claim 2, wherein, when thereleasable connection is released, the opening is formed between twosubregions of the antenna element held away from one another by therelease of the releasable connection.
 20. The local coil as claimed inclaim 3, wherein, when the releasable connection is released, theopening is formed between two parts of the antenna element held awayfrom one another by the release of the releasable connection, andwherein an instrument is passable through the opening.